Thermal-activated degradation mechanism on Phosphor-Converted Light Emitting Diode

An accelerated lifetime testing on low power Phosphor- Converted Light Emitting Diodes (pcLEDs) has been performed aiming at detecting the failure modes and evaluating the degradation law. The main actors involved in the current Solid State Lighting market are the light sources based on InGaN blue LEDs. Together with yellow phosphors for light conversion, these devices can ideally assure long lifetimes, high robustness and versatility in chromatic yield. Despite the efforts spent on improving the performances of such devices, the scientific community is still involved in obtaining a better thermal management for pcLEDs. The high temperature levels at the junction still limit the reliability of LED sources, most of all for low power devices not optimized for heat removal. A set of accelerated life testing setups for low power pcLEDs has been designed in order to understand the impact of bias and temperature on optical, electrical and thermal properties of such devices, and to identify the degradation mechanisms involved.